Not fresh water and nothing to buy for a fresh water tank but if you are going that way Santa Cruz has the Monarch butterflies roosting for the winter at Natural Bridges and Natural Bridges is very close to Long Marine Lab which is not large or expensive and is quite nice to visit.

My favorite LFS is TAT in Ventura off the 101. DH likes to eat at the Japanese market next door and I sneak over to look at the fish and multiple tanks of plants for sale and planted tanks in there.